Note: Descriptions are shown in the official language in which they were submitted.
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WHEELCHAIR WITH USER CONTROLLED TILT MECHANISM
Field of the Invention
[00011The present invention relates to a manual tilt wheelchair having a seat
that can be
tilted and, more particularly, to a manual wheelchair having a seat that can
be adjusted in its
angular orientation by the user without assistance by a caregiver.
Background of the Invention
[00021A tilt-in-space wheelchair provides the necessary change in position for
the user
who cannot effectively shift their body weight or change their position. These
individuals are at a
higher risk for skin breakdown and their sifting tolerance is compromised. A
typical tilt-in-space
wheelchair frame tilts up to 45 degrees from horizontal while maintaining the
same back to seat
angle. This feature provides a change in position for those people who have a
difficult time
maintaining their pelvic, trunk, and head position against gravity for
extended periods of time.
This feature can also assist in preventing postural collapse which puts them
at risk for respiratory
or digestive complications. Individuals who suffer from postural hypotension
also benefit from
tilt-in-space chairs.
[0003]Despite the fact that the wheelchair industry offers several models with
a tilting
seating system, no manual wheelchairs currently on the market are designed so
that the user can
tilt independently, that is, none can be tilted without the assistance of an
attending caregiver. Tilt
wheelchairs were designed so that the user's body can be angled at various
degrees so that
pressure points are redistributed and their upper body can be positioned for
optimal posture and
comfort. The existing manual tilt wheelchairs have to be activated by a
caregiver with the
control located in the back of the chair, or to the side, out of the users
reach. They are also
designed with the armrest and seat attached to each other, therefore, the
design does not give the
user a place to push and pull from to activate the tilt feature.
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[0004]The average wheelchair user spends 8-14 hours in their wheelchairs
daily. These
individuals who spend these extended hours in a static upright position often
end up needing
additional medical treatments. They are at risk for pressure ulcers, skin
tears, skeletal deformities
(specifically kyphosis or "C" curve posture), impaired respiration and
digestion from forward
flexed postures, joint contractures, pain and discomfort, agitation, decreased
mobility, and falls,
which can result in injuries.
[0005]For the average, able-bodied person, relief from discomfort during
prolonged
sitting is made by frequent, small, unconscious body adjustments that maintain
comfort levels.
For persons with physical disabilities and generalized muscle weakness, the
discomfort and pain
from daily wheelchair sitting can be chronic and debilitating. In addition to
the potential for
developing decubitus ulcers, many people in this population experience
intolerable periods of
discomfort and pain, which can lead to reduced participation in daily
activities including, work,
education, and recreation, and retrieval. (D. Hobson & Barbara Crane: State of
the Science White
Paper on Wheelchair Seating Comfort 2/9/01)
[0006]According to the National Pressure Ulcer Advisory Panel (NPUAP) the
treatment
costs for patients who developed ulcers were estimated to be as much as $6
billion per year. In
elderly populations and in those who are institutionalized, pressure ulcers
are one of the most
costly diseases to treat. These ulcers add an estimated burden of over $1
billion in expenditures
and an additional 2.2 million Medicare hospital days to the United States
healthcare system. The
bottom line alone, without considering the cost of human suffering,
demonstrates the importance
of preventing pressure ulcers.
[0007]Accordingly, it would be advantageous to have a manual wheelchair with a
user
controlled seat tilt mechanism that can be readily operated by the user while
sitting in the
wheelchair without the need for assistance of a caregiver so as to allow the
user to make desired
adjustments to the angular orientation of the seat of the wheelchair.
Summary of the Invention
[0008]The present invention is therefore directed to a manual wheelchair where
the user
has full control of the tilt angle of the wheelchair seat. As used herein the
term "user" will mean
the patient or person actually seated in and supported by the wheelchair. As
also used herein, the
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wheelchair is described as a "manual wheelchair" and that means that the
wheelchair is propelled
solely by the user and no external motive system is employed.
[00091With the present invention, the user can independently perform the tilt
operation on
the wheelchair so that the user can execute pressure relief and postural
changes throughout the
day in order to maintain optimal comfort and skin integrity during the many
hours spent in the
wheelchair without assistance from a caregiver.
[00101The wheelchair is designed to have a base frame with a seat that pivots
backward
and forward with respect to the base frame and is also provided with a user
controlled actuator
that can be released to allow the seat to freely tilt about the base frame as
well as to again lock
the seat in the desired tilt angle selected by the user.
[00111Unlike other tilt wheelchairs, the armrests of the present manual
wheelchair are
fixed to the base frame instead of the seat in order to provide the user with
a fixed structure to
push and pull against while tilting the seat. This allows the user to operate
a controller that is
located proximate to at least one of the arm rests to allow the user to use
the stability of one or
both of the armrests to tilt the seat by pushing and/or pulling on an armrest
for leverage to
independently tilt the seat of the wheelchair. Releasing the controller
automatically relocks the
system into position. No assistance is required from a caregiver to adjust the
angle of the seat of
the wheelchair.
[001210ther features of the tilt mechanism of the present invention will
become more
apparent in light of the following detailed description of a preferred
embodiment thereof and as
illustrated in the accompanying drawings.
Brief Description of the Drawings
[00131Figure 1 is a side view of a wheelchair having the tilt mechanism of the
present
invention with the seat in its upright position;
[00141Figure 2 is a side view of the wheelchair of Fig. 1 with the seat in its
tilted
position;
[00151Figure 3 is an enlarged perspective view illustrating the pivot point
for the seat;
[00161Figure 4 is a schematic view illustrating the control system for a
hydraulic cylinder
used with the tilt mechanism of the present invention; and.
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[00171Figure 5 is a side view of the wheelchair of Fig. 1 illustrating the
system for
compensating for the weight of a user.
Detailed Description of the Invention
[00181Referring to Figs. 1 and 2, there is shown side views of a wheelchair 10
having a
tilt mechanism constructed in accordance with the present invention. As can be
seen, the
wheelchair 10 is made up of a base frame 12 that may include lower horizontal
members 14 as
well as upper horizontal members 16 joined by vertical members 18. As will be
described, only
one side of the wheelchair 10 that appears in Figs. 1 and 2 will be described,
however it is well
known that an opposite side of the wheelchair 10 is present and which is
similar to or a mirror
image of the side shown in Figs. 1 and 2.
[00191There may also be conventional wheels 20 located at the bottom of the
base frame
12 to enable the wheelchair 10 to be freely movable along a planar surface.
[00201A pair of drive wheels 22 are also provided (again, only one of which is
shown in
the Figures) and which enable the user to move the wheelchair 10 in a desired
direction and the
drive wheels 22 may be grasped by the user of the wheelchair 10 or by a
caregiver, or by some
other propulsion system so as to cause rotation of the drive wheels 22 to move
the wheelchair 10.
[00211A seat 24 is pivotally affixed to the base frame 12 so as to be
rotatable about a
pivot point in order to allow the seat 24 to be tilted to a desired
orientation. In an exemplary
embodiment, the seat 24 is comprised of a seat frame including a bottom seat
frame member 26
and a back seat frame member 28 that are generally L-shaped so that the seat
24 can comfortably
accommodate and support a user.
[0022]The bottom seat frame member 26 and back seat frame member 28 can be
individual members affixed together or can be a unitary member that is bent
into the proper
shape. Again, as is conventional, there is a similar bottom seat frame member
and back seat
frame member located on the opposite side to the wheelchair 10 as well as
horizontal members
that are secured together in making up the seat 24.
[0023]There is also included a head rest 30 and a bottom cushion 32 for the
comfort of
the user and which are affixed to frame members of the seat 24. The seat 24
may also include a
leg rest 34 that includes a leg cushion 36, again, for the comfort of the
user.
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[0024]As can now be seen, the seat 24 is affixed to the base frame 12 such
that the seat 24
pivots about a pivot point 38 while retaining its L-shaped configuration to
support the user.
[0025]Turning briefly to Fig. 3, taken along with Figs. 1 and 2, there can be
seen an
enlarged perspective view of the pivot point 38 where the seat 24 is pivotally
affixed to the base
frame 12. In Fig. 3 there can be seen a cross member 40 that spans the width
of the wheelchair
and connects to the bottom seat frame members 26 on each side of the
wheelchair 10.
[00261A coupling 42 connects the cross member 40 to each bottom seat frame
member 26
so that the bottom seat frame member 26 can rotate with respect to the cross
member 40 in order
to allow the seat 24 to tilt with respect to the base frame 12.
[0027]As can now be seen, the seat 24 can pivot about the pivot point 38 to
enable the
seat 24 to move to various tilt positions and, in Fig. 1, the seat 24 is in
the upright position and in
Fig. 2, the seat 24 has been moved to a tilted position. In an exemplary
embodiment, the tilt
angle A (Fig. 2) of the seat 24 between its upright position and its maximum
tilt position is about
45 degrees.
[0028]The present invention includes a tilt mechanism that allows the user to
control the
amount of tilt of the seat 24. As previously explained, the tilting of the
seat 24 is controllable by
the user by simply grasping onto the arm rest 44 and using that grip on the
arm rest 44 as a steady
site to move the seat 24 to the desired tilt angle. The arm rest 44 is not
movable with respect to
the seat 24 but is fixed with respect to the base frame 12. In this manner,
the user can grip the
immovable arm rest 44 and use it for leverage to tilt the seat 24 about the
pivot point 38 to the
desired tilt angle.
[002910nce the desired tilt angle A has been attained, the tilt mechanism
allows the user
to lock the seat 24 firmly at that tilt angle. As such, the tilt mechanism
includes a linear actuator
46 that is connected between the seat 24 and the base frame 12. In the
exemplary embodiment,
the linear actuator can be a locking gas spring and one conventional locking
gas spring that can
be used is commercially available from Suspa Holding GmbH of Altdorf, Germany.
Such
locking gas spring is a combination spring and locking mechanism. The linear
actuator 46 of the
exemplary embodiment comprises an outer cylinder 48 and a piston 50 movably
located therein.
The linear actuator 46 has one end 52 affixed to the seat 24 at a location 54
along the bottom seat
frame member 26 that is displaced a linear distance away from the pivot point
38 and the other
end 56 is attached at a fixed location 58 with respect to the base frame 12.
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[0030]The fixed location 58 is on a support bracket 60 that is solidly affixed
to the base
frame 12 and the support bracket 60 is an arcuate or curved bracket having a
plurality of
openings 62 formed therealong. Accordingly, the other end 56 of the hydraulic
cylinder 46 can
be attached to the support bracket 60 at any of the openings 62 so that the
hydraulic cylinder 46
can be set in order to compensate or adjust for the weight of the user. With
the use of the support
bracket 60, the other end 56 of the linear actuator 46 can be affixed to a
selected opening 62 in
the support bracket 60 depending upon the weight of the user.
[0031]Accordingly, as the seat 24 is tilted by the user, the piston 50 moves
inwardly or
outwardly with respect to the outer cylinder 48 to contract or extend the
liner actuator 46. The
movement of the piston 50 is controlled so that it can be allowed to freely
move or be prevented
from movement such that the angle A of the seat 24 can also be controlled,
that is, when the
piston 50 is free to move within the outer cylinder 48, the seat 24 can be
moved by the user to a
desired tilt angle and when the piston 50 is prevented from moving within the
outer cylinder 48,
the seat 24 will be retained and held in whatever angle has been set by the
user.
[0032]Turning then to Fig. 4, there is shown a schematic view of an exemplary
system
that can be used to control the movement or non-movement of the piston 50
within the outer
cylinder 48. As can be seen, the hydraulic cylinder 46 includes the outer
cylinder 48 and the
piston 50 having a piston head 64. A hydraulic line 66 is shown in dotted
lines and which forms
a closed loop between a port 68 on one side of the piston head 64 and another
port 70 that is
located on the other side of the piston head 64. As such, as the piston 50
moves in either
direction within the outer cylinder 48, the hydraulic fluid readily flows
through the closed loop of
the hydraulic line 66 such that the piston 50 is free to move within the outer
cylinder 48.
[0033]There is, however, a controller 72 that can be activated by the user to
close the
hydraulic line 66 by pinching the hydraulic line 66 to stop the flow of
hydraulic fluid therein, and
which renders the piston 50 immovable within the outer cylinder 48.
[0034]As such, the controller 72 may include a pinch member 74 that is spring
biased by
means of a spring 76 to its closed position pinching the hydraulic line 66 to
prevent movement of
the piston 50 within the outer cylinder 48. The controller 72 may comprise a
lever 78, operable,
by the user of the wheelchair 10 to move the pinch member 74 against the bias
of spring 76 to
open the hydraulic line 66 to allow the piston 50 to move within the outer
cylinder 48.
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[0035]The controller 72 can be located on the wheelchair 10 within ready reach
of the
user of the wheelchair 10 proximate to the arm rest 44, such as attached to
the arm rest 44 so that
the user can simply move the actuator 72 to its open position to open the
hydraulic line 66 so that
the piston 50 can move and the user can adjust the tilt angle of the seat 24
to any desired position
using the leverage of the arm rest 44. By locating the controller 72 proximate
to the arm rest 44,
the user can release the controller 72 and then, since the arm rest 44 is
fixed with respect to the
base frame 12 and therefore does not move when the seat 44 is tilted, the user
can use the
leverage provided by the fixed arm rest 44 to push or pull on the arm rest 44
to move the seat 24
to the desired tilt angle.
[0036]As can be seen, while the present controller 72 controls the flow of
hydraulic fluid
to allow the piston 50 to move and to be prevented from moving, other types of
controllers can
be used, including air activated controllers that are activated by the breath
of a user.
[00371 When the user has the seat 24 in the desired tilt angle, the user
simply releases the
actuator 72 so that the actuator 72 moves the actuator 72 to its closed
position and stops the flow
of the hydraulic fluid in the hydraulic line 66 and thereby holds the piston
50 in that exact
position thereby retaining the angular orientation of the seat 24 as desire by
the user.
[0038]According as can now be seen, the patient or user has full control of
the angular tilt
of the seat 24 and the user can simply activate the actuator 72 to open the
flow of hydraulic fluid
in the hydraulic line 66 to allow the user to move the seat 24 to any desired
tilt angle, and, when
that tilt angle has been realized, the user can release the actuator 72,
thereby stabilizing the piston
50 and the seat 24 to maintain the particular tilt angle.
[00391Turning to Fig. 5, there is shown a side view of the wheelchair 10 with
the seat 24
in its upright position. In Fig. 5, there can be seen a controller 80 that is
positioned at a location
that is convenient to the user and is pivotally affixed to a stmt 82 that is
fixed to the arm rest 44
at a pivot point 84 on that strut 82. In the location as shown, the controller
80 is located so that
the user can operate the controller 80 to control the tilt angle of the seat
24. Due to the location
of the controller 80 proximate to and just underneath the arm rest 44, the
user can activate the
controller 80 while gripping the arm rest 44 to use the arm rest 44 to move
the seat 24 to the
desired tilt angle, and then release the controller 80 to retain the seat 24
at that angle.
[0040]The present invention also includes a compensation system to compensate
or adjust
for the weight of the user seated in the seat and that compensation system can
be carried out in
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different ways. One way is to change location of the pivot point 38 with
respect to the base
frame 12. In the exemplary embodiment, the location of the pivot point 38 can
be moved (see
Fig. 3) by loosening the coupling 42 and simply moving the coupling 42 along
the bottom seat
frame member 26 and re-tightening the coupling when the pivot point 38 has
been moved to a
desired position. By moving the pivot point 38 forward and rearward,
compensation can be
made for the weight of the user. If the user seated in the wheelchair 10 is
light, the pivot point 38
can be moved forward; if heavy, the pivot point 38 can be moved rearwardly.
[00411In addition, as explained, the other end 56 of the hydraulic cylinder 46
can be
moved with respect to the base frame 12 to a selected opening 62 in the
support bracket 60. For
a light user, an opening can be selected in the upper part of the support
bracket and, for a heavier
user, the selected opening 62 can be moved to a lower located opening 62.
[00421While the present invention has been set forth in terms of a specific
embodiment,
or embodiments, it will be understood that the present tilt mechanism for a
wheelchair herein
disclosed may be modified or altered by those skilled in the art to other
configurations.
Accordingly, the invention is to be broadly construed and limited only by the
scope and spirit of
the claims appended hereto.
